Insect control sheet

ABSTRACT

An insect control sheet containing a Cry polyhedron prepared by fixing an insecticidal protein (a Cry toxin) produced by Bacillus thuringiensis to a polyhedron of polyhedrin protein is provided. The insect control sheet contains the Cry polyhedron and is used by floating on water. The insect control sheet is floatable on water, and includes a pure matrix layer  20  and a toxin-containing matrix layer  30  containing the Cry polyhedron  51  which are layered on the underside of a sheet-shaped first sheet substrate  10 . The pure matrix layer  20  is composed of a degradable or water-soluble second material and the toxin-containing matrix layer  30  is composed of a degradable or water-soluble third material and the Cry polyhedron. The toxin-containing matrix layer sustainably releases the Cry polyhedron to the water on which the insect control sheet is floated.

TECHNICAL FIELD

The present invention relates to an insect control sheet used byfloating on water.

BACKGROUND ART

The insecticidal protein produced by Bacillus thuringiensis (hereinafterreferred to as a “Cry toxin”) exerts an insecticidal activity againstcertain species of insects. The Cry toxin produced by Bacillusthuringiensis serovar israelensis is known to be toxic to mosquitolarvae.

The inventors fixed the Cry toxin to a polyhedron of polyhedrin protein,which is a protein microcrystal produced by Bombyxmori cypovirus(BmCPV). The Cry toxin fixed to the polyhedron is hereinafter referredto as a “Cry polyhedron”. A tag for fixing the Cry toxin to thepolyhedron of polyhedrin protein was added to the N-terminal of the Crytoxin. Then the tagged Cry toxin was fixed to the polyhedron ofpolyhedrin protein.

The inventors reported that

-   -   (1) the Cry polyhedron exerted an insecticidal activity against        mosquito larvae, and    -   (2) mosquito larvae which ingested the Cry polyhedron died        (refer to the non-patent literature 1).

On the other hand, a method for making mosquito larvae easily ingest theCry polyhedron at their habitat in natural environment was not found atthat time.

CITATION LIST Non-Patent Literature

NPL 1: HARADA Yoshihiro, KOTANI Eiji, ASANO Shin-ichiro, & MORI Hajime,“Fixation of the δ-endotoxins of Bacillus thuringiensis to polyhedra andapplication thereof”, A6 in “The collection of the lectures in Kansaiarea”, distributed at “the Academic Lectures for the Study and Use ofInsect Functions”, the Joint Meeting of the Japanese Society ofSericultural Science, Nov. 10, 2012

SUMMARY OF INVENTION Technical Problem

The problems to be solved by the invention is fabricating insect controlsheets and articles containing the Cry polyhedron as the activeingredient, and harmful insects easily ingesting the Cry polyhedron, andalso finding a means of the same.

Other problems to be solved by the present invention are apparentlyexplained in the following description of the present invention.

Solution to Problem

The means for solving the problems will be described below. The signsused in the description correspond to the signs in the embodiments ofthe present invention for the convenience of understanding, and thepresent invention is not restricted within the scope of the embodiments.The numbers used as the signs may collectively represent the parts, andalphabetical letters are sometimes added to the numbers to representeach of the parts in the working examples mentioned below.

An insect control sheet according to an embodiment of the presentinvention comprises an insecticidal protein produced by Bacillusthuringiensis (hereinafter referred to as a “Cry toxin”) and fixed to apolyhedron of polyhedrin protein (the Cry toxin fixed to the polyhedronhereinafter referred to as a “Cry polyhedron”), and is used by floatingon water surface. The insect control sheet comprises a sheet-shapedfirst sheet substrate(10), a pure matrix layer (20) layered on theunderside of the first sheet substrate (10), and a toxin-containingmatrix layer (30) containing the Cry polyhedron (51) and layered on theunderside of the pure matrix layer, and the insect control sheet floatson water. Also, the insect control sheet comprises,

-   -   the pure matrix layer is composed of a degradable or        water-soluble second material,    -   the toxin-containing matrix layer is composed of a degradable or        water-soluble third material and the Cry polyhedron; and    -   the toxin-containing matrix layer sustainably releases the Cry        polyhedron to the water on which the insect control sheet is        floated.

Harmful insects include those killed by the Cry toxin, for example,insects falling into Diptera, Coleoptera and Lepidoptera.

Mosquito larvae (called “bofura” or “bofuri” in Japanese) falling intothe category of harmful insects usually float in water between watersurface and several centimeters below water surface. Mosquito larvaeregularly go up to water surface to breathe and feed in water. The Crypolyhedron has a specific gravity of 1.27.

A suspension of the Cry polyhedron may come to one's mind as a Crypolyhedron-containing insecticide to kill mosquito larvae. However, theCry polyhedron soon settles out after addition of the suspension towater without remaining within several centimeters below water surface,and fails to provide mosquito larvae the chance of ingestion. Thus thesuspension of the Cry polyhedron cannot effectively exert itsinsecticidal activity against mosquito larvae.

The insect control sheet of the present invention

-   -   (1) floats on water surface, and    -   (2) comprises, in addition to other elements, the        toxin-containing matrix layer composed of the degradable or        water-soluble third material and the Cry polyhedron. The        toxin-containing matrix layer sustainably releases the Cry        polyhedron to the water on which the insect control sheet is        floated. Consequently the Cry polyhedron is constantly supplied        to the habitat, namely feeding place, of mosquito larvae, and        exerts its insecticidal activity against mosquito larvae which        ingest the Cry polyhedron.

The insect control sheet according to a preferred embodiment of thepresent invention may include the second material composed of the sameingredients as that of the third material. The third material may becomposed of specific ingredients.

The specific ingredients have low human health risks to make the insectcontrol sheet preferable to be used in a water tank for daily life waterincluding drinking water.

Another insect control sheet according to a preferred embodiment of thepresent invention includes the first sheet substrate composed of adegradable first material. The toxin-containing matrix layer and thepure matrix layer may degrade or dissolve in water in a shorter timethan that required for the decomposition or dissolution of the firstsheet substrate.

The insect control sheet of the preferred embodiment is composed of theelements all of which degrade or dissolve in water. The sheet substrateretains its form throughout the period in which the toxin-containingmatrix layer releases the Cry polyhedron, and thus enables thesustainable release of the Cry polyhedron from the degradable insectcontrol sheet.

The insect control sheet of the preferred embodiment has the advantagethat the sheet leaves no residue after use.

An insect control sheet according to another preferred embodiment of thepresent invention may include the first sheet substrate composed ofnonwoven fabric or mesh sheet. The first sheet substrate composed ofnonwoven fabric or mesh sheet has the advantage that such materialincreases the amount of the Cry polyhedron retained per unit area of thefirst sheet substrate. In addition, the porous structure of nonwovenfabric or mesh sheet enables easy manufacture of a floatable body byfilling the first sheet substrate with bubbles.

The first sheet substrate may be a flat plate including plates, thinplates, sheets and films. One side or both sides of the flat plate maybe smooth, or may be wholly or partially rough.

An insect control sheet according to another preferred embodiment of thepresent invention has a floating member for floating the insect controlsheet on water which is bubbles or air cells contained in one of memberscomprising the insect control sheet.

In other words, the insect control sheet may include the first sheetsubstrate containing bubbles, a sheet-shaped second sheet substratecontaining bubbles and layered on the top side of the first sheetsubstrate, and the toxin-containing matrix layer containing bubbles. Inaddition the first sheet substrate may be composed of two layers betweenwhich air cell is formed.

An insect control sheet according to yet another preferred embodiment ofthe present invention has a floating member for floating the insectcontrol sheet on water which is a hydrophobic region formed on thesurface of the insect control sheet.

In other words, the insect control sheet may include a patternedhydrophobic region formed on the underside of the first sheet substrateand the pure matrix layer and the toxin-containing matrix layer layeredon the part of the underside of the first sheet substrate where thehydrophobic region is not formed. The insect control sheet may alsoinclude the hydrophobic region formed on the top side of the first sheetsubstrate.

Another insect control sheet according to a preferred embodiment of thepresent invention may include a design made on the underside of thefirst sheet substrate.

The design is made by printing or drawing, and the examples of thedesign are letters and graphics. The design may represent, for example,a sign indicating the time for the replacement of the insect controlsheet or a caution for proper hygiene

For example, the hydrophobic part patterned on the underside of thefirst sheet substrate mentioned above may be formed into a designincluding letters and graphics. The hydrophobic part may also be formedinto a part of such letters and graphics. In addition, the design on theunderside of the first sheet substrate may be covered with the purematrix layer and the toxin-containing matrix layer to be hidden beforethe insect control sheet is used, and may appear after the use of theinsect control sheet for a certain period as the result of thedisappearance caused by the decomposition or the dissolution of thetoxin-containing matrix layer and the pure matrix layer.

The method of exposing the design after the use of the insect controlsheet for a certain period may include the use of the second and thirdmaterials colored with dyes. Edible dyes are preferable for coloring theinsect control sheet used in a water tank of daily life water includingdrinking water.

An insect control article being used by floating on water according toanother embodiment of the present invention comprises a body floatableon water,

-   -   a pure matrix layer layered on the underside of the body, and    -   a toxin-containing matrix layer layered on the underside of the        pure matrix layer.

The insect control article also comprises:

-   -   the pure matrix layer comprises a degradable or water-soluble        second material;    -   the toxin-containing matrix layer comprises a degradable or        water-soluble third material and the Cry polyhedron; and    -   the toxin-containing matrix layer sustainably releases the Cry        polyhedron to the water on which the insect control article is        floated.

A transfer sheet according to another embodiment of the presentinvention is used to fabricate the insect control sheet or insectcontrol article. The transfer sheet comprises the toxin-containingmatrix layer containing the Cry polyhedron, the pure matrix layer, andan adhesive layer layered in the order on one surface of atransfer-sheet substrate. Also, the transfer sheet comprises;

-   -   the toxin-containing matrix layer comprising a degradable or        water-soluble third material and the Cry polyhedron; and    -   the pure matrix layer comprising a degradable or water-soluble        second material.

The present invention, preferred embodiments of the present inventionand the elements contained therein can be combined as far as possible towork the invention.

Advantageous Effects of Invention

The insect control sheet according to one embodiment of the presentinvention includes the toxin-containing matrix layer composed of thedegradable or water-soluble third material and the Cry polyhedron andthe pure matrix layer sandwiched between the first sheet substrate andthe toxin-containing matrix layer, in addition to other elements.

Owing to the structure, the Cry polyhedron is gradually released intowater connected with the degradation or dissolution of thetoxin-containing matrix layer. In addition, the pure matrix layerprevents the Cry polyhedron from contacting with the first sheetsubstrate so as to facilitate release of the Cry polyhedron.

The insect control article according to another embodiment of thepresent invention includes the toxin-containing matrix layer composed ofthe degradable or water-soluble third material and the Cry polyhedron,and the pure matrix layer sandwiched between the underside of the bodyand the toxin-containing matrix layer, in addition to other elements.

Owing to the structure, the Cry polyhedron is gradually released intowater connected with the degradation or dissolution of thetoxin-containing matrix layer. In addition, the pure matrix sheetprevents the Cry polyhedron from contacting with the first sheetsubstrate so as to facilitate release of the Cry polyhedron.

The transfer sheet according to another embodiment of the presentinvention includes, in addition to other elements, the toxin-containingmatrix layer containing the Cry polyhedron, the pure matrix layer, andthe adhesive layer layered in this order on one surface of thetransfer-sheet substrate. Thus the transfer sheet can be used totransfer the layers from the transfer-sheet substrate to the first sheetsubstrate or the body of any forms and properties, and advantageouslyused to fabricate an insect control sheet or article having the layersof properly controlled thickness and uniformity.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view illustrating the first insect control sheet 1a.

FIG. 2 is a sectional view illustrating the second insect control sheet1 b.

FIG. 3 is a sectional view illustrating the third insect control sheet 1c.

FIG. 4 is a sectional view illustrating the fourth insect control sheet1 d.

FIG. 5 is a sectional view illustrating the fifth insect control sheet 1e.

FIG. 6 is a sectional view illustrating the sixth insect control sheet 1f.

FIG. 7 is a sectional view illustrating the seventh insect control sheet1 g.

FIG. 8 is a sectional view illustrating the insect control article.

FIG. 9 is a sectional view illustrating the transfer sheet forfabricating the insect control article.

FIG. 10 is a sectional view illustrating the eighth insect control sheet1 h.

FIG. 11 is a sectional view illustrating the ninth insect control sheetli.

DESCRIPTION OF EMBODIMENT

The insect control sheet, insect control article, and transfer sheetaccording to the embodiments of the present invention are furtherdescribed below referring to the figures. Some of the figures referredherein are schematic diagrams containing magnification of some elementsfor easy understanding of the present invention. Thus some of thedimensions or dimensional ratio between the elements may be differentfrom that of the actual sheets and articles.

In the sectional views showing the layer structure, the blank betweenthe layers is made for the convenience of explanation of the layerstructure. In the actual insect control sheets or insect controlarticles, the layers are attached to each other.

The dimensions, materials, forms, and relative positions of the membersand parts described in the working examples of the present inventionmerely explain the present invention and are not intended to restrictthe scope of the present invention unless otherwise specified.

FIG. 1 is a sectional view illustrating the first insect control sheet 1a.

The first insect control sheet la includes the pure matrix layer 20layered on the underside of the first sheet substrate 10 and thetoxin-containing matrix layer 30 layered on the underside of the purematrix layer 20.

In the present invention and in this specification, the top side andunderside are defined for the explanation. When the insect control sheetis placed on water, the side contacting with water or sinking into wateris defined as the underside while the side facing the atmosphere isdefined as the top side. This applies to the insect control sheets fromthe second to ninth and the insect control article explained below.

The first sheet substrate 10 is a support member for the pure matrixlayer 20 and the toxin-containing matrix layer 30. The first sheetsubstrate 10 is composed of the first material. The first material maybe degradable, water-soluble, persistent, or poorly water soluble. Thefirst material should preferably be degradable or water-soluble in termsof the protection of natural environment. The first material shouldpreferably have low human health risks, because the insect control sheetmay be used to control harmful insects in a water tank reserving dailylife water.

The first sheet substrate has a sheet shape extending two-dimensionally.The sheet shape extending two-dimensionally includes, for example,sheet, film and paper. The thickness of the first sheet substrate is notspecifically restricted, and preferably ranges from 16 μm (micrometers)to 3 mm (millimeters). A thickness within the range gives sufficientstrength to the first sheet substrate and enables the pure matrix layer20 and the toxin-containing matrix layer 30 to be readily layered. Inaddition, the first sheet substrate having such thickness facilitatesdesigning of the time required for the decomposition of degradablematerials in natural environment.

The two-dimensional size of the first sheet substrate is notspecifically restricted, and may be determined according to the area ofwater surface in a water tank to which the insect control sheet isplaced.

The pure matrix layer 20 separates the toxin-containing matrix layer 30and the first sheet substrate 10. If the Cry polyhedron contained in thetoxin-containing matrix layer contacted with the first sheet substrate,the Cry polyhedron would adhere to the first sheet substrate and wouldnot be easily released from the first insect control sheet.

For solving the trouble mentioned above, the insect control sheetincludes the pure matrix layer 20 which separates the toxin-containingmatrix layer 30 and the first sheet substrate 10 to secure the releaseof the Cry polyhedron.

The pure matrix layer 20 is composed of the degradable or water-solublesecond material. The second material should preferably have low humanhealth risks, because the insect control sheet may be used to controlharmful insects in a water tank reserving daily life water. Thethickness of the pure matrix layer is not specifically restricted, andcan be optionally determined, preferably within the range from 5 nm(nanometers) to 50 μm (micrometers). A thickness within the rangeenables the separation of the toxin-containing matrix layer 30 and thefirst sheet substrate 10.

The pure matrix layer 20 can be formed by coating, printing or dipping.

The term “pure” of the pure matrix layer 20 means that the layer is freeof toxins. With this concept, the matrix layer containing toxins iscalled “the toxin-containing matrix layer 30”. The material constitutingthe pure matrix layer 20 does not mean “a pure material purified byremoving impurities to the utmost limit”.

The toxin-containing matrix layer 30 is composed of the degradable orwater-soluble third material and the Cry polyhedron. Thetoxin-containing matrix layer 30 releases the Cry polyhedron caused bythe decomposition or dissolution of the third material.

The toxin-containing matrix layer 30 is composed of the degradable orwater-soluble third material. The third material should preferably havelow human health risks, because the insect control sheet may be used tocontrol harmful insects in a water tank reserving daily life water. Thethickness of the toxin-containing matrix layer 30 is not specificallyrestricted, and may be optionally determined preferably within the rangefrom 5 nm (nanometers) to 1 mm (millimeter). A thickness within therange enables the release of the Cry polyhedron. The lower limit of thethickness, 5 nm (nanometers), is the thickness of the part of thetoxin-containing matrix layer where only the third material constitutesthe matrix layer (the part where the Cry polyhedron is not contained).

The Cry polyhedron is produced by fixing the Cry toxin to a polyhedronof polyhedrin protein, which is a protein microcrystal produced byBombyxmori cypovirus (BmCPV). A tag for fixing the Cry toxin to thepolyhedron of polyhedrin protein is added to the N-terminal of the Crytoxin. Then the tagged Cry toxin is fixed to the polyhedron ofpolyhedrin protein. In the method, the Cry toxin can be fixed to thepolyhedron by adding the N-terminal α-helix H1 (refer to Reference C-1)of the polyhedrin protein to the N terminal of the Cry toxin. Thepolyhedron, which solubilizes at a pH of 10 or more, functions as acarrier suitable for the Cry toxin, because the polyhedron solubilizesunder the alkaline condition in the digestive tract of mosquito larvae(refer to Reference C-2). The diameter of the circumscribed sphere ofthe Cry polyhedron, which represents the size of the Cry polyhedron,ranges from 3 μm (micrometers) to 15 μm (micrometers).

The Cry toxin fixed to the Cry polyhedron and contained in thetoxin-containing matrix layer is an insecticidal protein usuallyproduced by bacteria included in Bacillus thuringiensis and itsvarieties or subspecies. Preferable Cry toxins are Cry11Aa, Cry4Aa,Cry4Ba, and Cry10Aa produced by Bacillus thuringiensis serovarisraelensis, and Cry11Aa is more preferable.

Cry11Aa is highly toxic to the larvae of Aedes which transmit arbovirusincluding dengue virus, Culex which transmit filaria, and Anopheleswhich transmit plasmodium (refer to Reference C-3).

Reference

Reference C-1: Hiroshi Ijiri, Fasseli Coulibaly, Gento Nishimura et al.,Structure-based targeting of bioactive proteins into cypovirus polyhedraand application to immobilized cytokines for mammalian cell culture,Biomaterials 30 (2009) 4297-4308

Reference C-2: Despres Laurence, Lagneau Christophe & Frutos Roger,Using the Bio-Insecticide Bacillus thuringiensis israelensis in MosquitoControl, Pesticides in the Modern World—Pests Control and PesticidesExposure and Toxicity Assessment, Edited by Dr. Margarita Stoytcheva,Publisher In tech, September, 2011

Reference C-3: Jesko Oestergaad, Ralf-Udo Ehlers, Amparo C.Martinerz-Ramirez et al., Binding of Cyt1Aa and Cry11Aa Toxins ofBacillus thuringiensis Serovar israelensis to Brush Border MembraneVesicles of Tipula paludosa (Diptera: Nematocera) and Subsequent PoreFormation, Applied and Environmental Microbiology, Vol. 73, No. 11,(June 2007) 3623-3629

The toxin-containing matrix layer 30 can be formed by coating orprinting with a mixture prepared by mixing the third material and theCry polyhedron.

The first insect control sheet la floats on water, and sustainablyreleases the Cry polyhedron into the habitat of mosquito larvae betweenwater surface and several centimeters below water surface to makemosquito larvae ingest the Cry polyhedron.

The Cry polyhedron is sustainably released into water from thetoxin-containing matrix layer 30 when the first insect-control sheet 1 ais placed on water surface.

The first material is a constituent of the first sheet substrate 10.Examples of the degradable or water-soluble first material includestarches and starch mixtures with polylactic acid, chitin, chitosan,polyhydroxyalkanoates, polybutylene succinate, cellulose and protein;and natural fibers (cotton, wool, hemp, pulp, silk, kenaf, banana fiberand bamboo fiber) and their blends. These examples have low human healthrisks.

Examples of the persistent first material include resin sheets ofpolypropylene resins, polyethylene resins, polyamide resins, polyesterresins, acrylic resins, polyvinyl chloride resins, polycarbonate resins,polyurethane resins, polystyrene resins, and acetate resins; cellulosesheets, such as glassine paper, coated paper, and cellophane; andcomposites of those materials.

The third material is a matrix material constituting thetoxin-containing matrix layer 30. Examples of the third material includecollagen, gelatin, chitin, chitosan, glycosaminoglycan, hyaluronic acid,chondroitin sulfate, elastin, fibronectin, laminin, fibrin, alginicacid, fibroin, starch, pectin, pectic acid, agarose, heparin,carboxymethyl cellulose, cellouronic acid, polyvinyl alcohol,polyethylene glycol, methyl polymethacrylate, methacrylate esterpolymers, silicone resins, polylactic acid, polyglycolic acid,polyε-caprolactone, bovine serum albumin, casein, sucrose, and themixtures, polymers, copolymers and cross-linked products of thosesubstances. These examples have low human health risks.

The second material is a constituent of the pure matrix layer 20.Examples of the second material are the same as that mentioned in thedescription of the third material.

The second and third materials for the first insect control sheet 1 ashould preferably consist of the same ingredients, because thedegradation time of the toxin-containing matrix layer 30 and the purematrix layer 20 can be easily designed in designing the first insectcontrol sheet 1 a. In addition, the first insect control sheet 1 a canbe produced with a smaller number of materials and in a simpler processwhich enable easier process control.

The sheet substrate 10 of the first insect control sheet 1 a shouldpreferably be composed of the degradable first material, and the secondand third materials should preferably degrade or dissolve in waterfaster than the first material, because the second and third materialshaving such properties ensure that all of the Cry polyhedron containedin the toxin-containing matrix layer 30 will be gradually released.

The time required for the toxin-containing matrix layer 30 to degrade ordissolve in water should range usually from 15 days to 90 days,preferably from 15 days to 60 days, and more preferably from 25 days to45 days.

The time required for the pure matrix layer 20 to degrade or dissolve inwater should range usually from the time 5 days shorter to the time 10days longer than the time required for the degradation or dissolution ofthe toxin-containing matrix layer, preferably from the time 3 daysshorter to the time 10 days longer, and more preferably from the time 1day shorter to the time 1 day longer. The time required for thedegradation or dissolution of the layers, however, cannot usually bedesigned by the day (24 hours), because the advancement of thedegradation or dissolution of the layers is influenced by watertemperature and quality which vary greatly. The degradation time istherefore forced to be set up roughly on a monthly basis. It ispreferable to design the time required for the degradation ordissolution of the two layers by employing the same material for thesecond and third materials to synchronize their degradation andcontrolling the thickness of the layers and concentration of thematerials in the layers.

The degradable or water-soluble first sheet substrate usually degradesor dissolves in water in 180 days and should preferably degrade ordissolves in the time from 30 days to 60 days longer than the timerequired for the toxin-containing matrix layer to degrade or dissolve inwater.

The first sheet substrate may be composed of nonwoven fabric or meshsheet.

The eighth insect control sheet 1 h schematically drawn in FIG. 10 iscomposed of the first sheet substrate 10 of nonwoven fabric. The surfaceof the nonwoven fabric is designed to form convexes and concaves whichare larger than the Cry polyhedron 51. Thus the insect control sheetcomposed of the first sheet substrate of nonwoven fabric retains greateramount of the Cry polyhedron per unit area than the insect control sheetcomposed of the first sheet substrate of a flat plate. In addition, theporous structure of nonwoven fabric facilitates the manufacture offloatable object where the first sheet substrate is aerated.

The diagram of the eighth insect control sheet 1 h in FIG. 10 shows thefirst sheet substrate 10, the pure matrix layer 20, and thetoxin-containing matrix layer 30 being attached to each other withouthaving a space between them.

The first material constituting the nonwoven fabric of the first sheetsubstrate 10 may be selected from various materials without anyrestriction. Natural fibers (cotton, wool, hemp, pulp, silk, kenaf,banana fiber, and bamboo fiber, etc.) are preferable for the firstmaterial because of their low human health risks.

The ninth insect control sheet 1 i schematically drawn in FIG. 11 iscomposed of the first sheet substrate 10 of mesh sheet. The surface ofthe mesh sheet is designed to form convexes and concaves which arelarger than the Cry polyhedron 51. Thus the insect control sheetcomposed of the first sheet substrate of mesh sheet retains greateramount of the Cry polyhedron per unit area than the insect control sheetcomposed of the first sheet substrate of a flat plate. In addition,porous structure of mesh sheet facilitates the manufacture of floatableobject where the first sheet substrate is aerated.

The diagram of the ninth insect control sheet 1 i in FIG. 11 shows thefirst sheet substrate 10, the pure matrix layer 20, and thetoxin-containing matrix layer 30 being attached to each other withouthaving a space between them.

FIG. 2 is a sectional view illustrating the second insect control sheet1 b. The second insect control sheet 1 b is different from the firstinsect control sheet 1 a in the property that the second insect controlsheet 1 b includes the first sheet substrate containing bubbles. Otherproperties such as the elements and the materials constituting thelayers are the same as that of the first insect control sheet 1 a. Thefirst sheet substrate, which makes the difference, is explained below.

The second insect control sheet lb includes the bubble-containing firstsheet substrate 10 a. The bubble-containing first sheet substrate 10 acontains a plurality of bubbles 16. Thus the bubble-containing firstsheet substrate 10 a has low specific gravity and decreases the specificgravity of the second insect control sheet 1 b to make the sheetfloatable on water.

The bubble-containing first sheet substrate 10 a is manufactured in theprocesses as exemplified below:

(1) Forming the first material into a sheet, holding the first materialsheet in a pressurized inert atmosphere to make the sheet contain theinert gas, and foaming the first material sheet by heating under normalpressure;

(2) Forming the first material into a sheet, simultaneously making thesheet contain water, and foaming the water-containing sheet by heating;or

(3) Making a bubble-containing material by adding a known blowing agentincluding hydrocarbons such as propane or ethers such as dimethyl etherto the first material.

FIG. 3 is a sectional view illustrating the third insect control sheet 1c. The third insect control sheet 1 c is different from the first insectcontrol sheet 1 a in the property that the third insect control sheetincludes the bubble-containing second sheet substrate 11 layered on thefirst sheet substrate 10. Other properties such as the elements and thematerials constituting the layers are the same as that of the firstinsect control sheet 1 a. The bubble-containing second sheet substrate,which makes the difference, is explained below.

The third insect control sheet 1 c includes the bubble-containing secondsheet substrate 11 layered on the top side of the first sheet substrate10. The bubble-containing second sheet substrate 11 contains a pluralityof bubbles 16. The bubble-containing second sheet substrate 11 has lowspecific gravity and decreases the specific gravity of the third insectcontrol sheet 1 c to make the sheet floatable on water.

The third insect control sheet 1 c is manufactured by, for example,forming the pure matrix layer 20 and the toxin-containing matrix layer30 on the first sheet substrate 10 and layering or bonding thebubble-containing second sheet substrate 11 on the top side of the firstsheet substrate 10.

The materials, foaming process, and degradation or dissolution time ofthe bubble-containing second sheet substrate 11 are the same as that ofthe first sheet substrate 10. The foaming process for thebubble-containing second sheet substrate 11 is the same as that forfoaming the bubble-containing first sheet substrate 10 a.

FIG. 4 is a sectional view illustrating the fourth insect control sheet1 d. The fourth insect control sheet 1 d is different from the firstinsect control sheet 1 a in the property that the fourth insect controlsheet 1 d includes the toxin-containing matrix layer containing bubbles.Other properties such as the elements and the materials constituting thelayers are the same as that of the first insect control sheet 1 a. Thebubble-toxin-containing matrix layer 30 a, which makes the difference,is mentioned below.

The bubble-toxin-containing matrix layer 30 a, one of the elements ofthe fourth insect control sheet 1 d, contains a plurality of bubbles 56and the Cry polyhedron 51. The bubble-toxin-containing matrix layer 30 ahas low specific gravity and decreases the specific gravity of thefourth insect control sheet 1 d to make the sheet floatable on water.

The bubble-toxin-containing matrix layer 30 a is manufactured in theprocesses as exemplified below:

(1) Adding bubbles, such as air bubbles, to a mixture of the thirdmaterial and the Cry polyhedron being knead, and hardening the mixture;and

(2) Manufacturing a bubble-containing material by adding a known blowingagent including hydrocarbons such as propane or ethers such as dimethylether to a mixture of the third material and the Cry polyhedron.

FIG. 5 is a sectional view illustrating the fifth insect control sheet 1e.

The fifth insect control sheet 1 e is different from the first insectcontrol sheet 1 a in the property that the fifth insect control sheet 1e includes the first sheet substrate having two layers between which aircells are contained. Other properties such as the elements and thematerials constituting the layers are the same as that of the firstinsect control sheet 1 a. The double-layered first sheet substrate,which makes the difference, is mentioned below.

The fifth insect control sheet 1 e include the first sheet substrate 10having tow layers composed of the top first sheet substrate 10 b and thebottom first sheet substrate 10 c. The top first sheet substrate 10 band the bottom first sheet substrate 10 c are partially separated toform air cells 15. Thus the first sheet substrate 10 composed of the topfirst sheet substrate 10 b and the bottom first sheet substrate 10 c haslow specific gravity to decrease the specific gravity of the fifthinsect control sheet 1 e so as to make the sheet floatable on water.

FIG. 5 shows the bottom sheet substrate 10 c, the pure matrix layer 20,and the toxin-containing matric layer 30 being attached to each other.

FIG. 6 is a sectional view illustrating the sixth insect control sheet 1f.

The sixth insect control sheet 1 f includes the hydrophobic region 13made into a pattern on the underside of the first sheet substrate 10,and also includes the pure matrix layer 20 and the toxin-containingmatrix layer 30 layered on the underside of the first sheet substratewhere the hydrophobic region is not made. The patterns of thehydrophobic region 13 include, for example, checkered patterns, latticedpatterns and dot patterns. The relative position of the hydrophobicregion and the layers including the pure matrix layer can be describedas an alternate arrangement.

Substances, especially sheet-shaped substances, coated with ahydrophobic material is floatable on water. The sixth insect controlsheet if has the hydrophobic regions on its underside which are formedpartially and exposed. Thus the sixth insect control sheet if isfloatable on water.

The hydrophobic region may be formed by spreading a hydrophobicmaterial. The hydrophobic region may also be formed by applying awater-repellent finish on the surface of the first sheet substrate 10.Examples of the hydrophobic material include fluorochemicalwater-and-oil repellent agents and particulate hydrophobic oxides (referto Reference C-4). Examples of the water-repellent finish includeembossing.

Reference

Reference C-4: JP 4348401

FIG. 7 is a sectional view illustrating the seventh insect control sheet1 g.

The seventh insect control sheet 1 g includes the hydrophobic regionformed on the first sheet substrate 10 in the same manner as that of thesixth insect control sheet 1 f. The hydrophobic region 13 of the seventhinsect control sheet 1 g is formed on the top side of the first sheetsubstrate. Other properties such as the elements and the materialsconstituting the layers are the same as that of the first insect controlsheet 1 a.

As shown in FIG. 7, the hydrophobic region 13 of the seventh insectcontrol sheet 1 g is formed on the top side of the first sheet substrate10. The hydrophobic region 13 is exposed on the outside of the seventhinsect control sheet 1 g to make the sheet floatable on water.

The hydrophobic region 13 may be formed all over the top side of thefirst sheet substrate 10 or on some part of the top side of the firstsheet substrate 10. Making the hydrophobic region all over the top sideis advantageous to easy forming of the hydrophobic region.

The design may be made on the underside of the first sheet substrate ofany of the insect control sheets of the first to the ninth. The designincludes letters and graphics, and may be made by printing, drawing, orembossing the surface of the first sheet substrate. Examples of thedesign include caution for the replacement of the insect control sheet,disposal methods for the first sheet substrate, and notice for properhygiene.

At the beginning of the use of the insect control sheet, the undersideof the first sheet substrate is covered with the pure matrix layer andtoxin-containing matrix layer which make the design invisible. At thefinal term of the use, the pure matrix layer and toxin-containing matrixlayer disappear to make the design visible and attract the attention ofthe user.

The design should preferably be printed or drawn with edible inks forthe insect control sheet used in a water tank of daily life waterincluding drinking water.

The pure matrix layer and/or the toxin-containing matrix layer may becolored to hide the design more effectively at the beginning of usingthe insect control sheet. The layers of the insect control sheet used ina water tank of daily life water including drinking water shouldpreferably be colored with food dyes.

FIG. 8 is a sectional view illustrating the insect control article.

The insect control article 6 includes the pure matrix layer 120 layeredon the underside, which contacts with water, of the body 117 floatableon water, and the toxin-containing matrix layer 130 containing the Crypolyhedron is layered on the underside of the pure matrix layer.

The pure matrix layer 120 is composed of the degradable or water-solublesecond material, and the toxin-containing matrix layer 130 is composedof the degradable or water-soluble third material and the Cry polyhedron51.

The materials and forms of the body 117 are not specifically restricted,and can be selected from any materials and forms which make the bodyfloatable on water and capable of sustainably releasing the Crypolyhedron 51 from the toxin-containing matrix layer layered on the body117. Examples of the forms and materials of the body 117 include woodenbodies of various forms and boat-shaped or lid-shaped bodies of metalsor synthetic resins.

The pure matrix layer is layered on the underside of the body whichcontacts with water.

The surface of the body 117 and the pure matrix layer 120 are bonded bythe adhesive layer 60. The materials of the adhesive layer includefibrin glue, gelatin glue, cyanoacrylates, urethane prepolymers,hydrogels, cross-linked polysaccharides, natural adhesive resins such asJapanese lacquer, mixtures of these materials, and mixtures of thesematerials and biodegradable resins. These materials mentioned here havelow human health risks.

The structure of the toxin-containing matrix layer 130 is the same asthat of the toxin-containing matrix layer 30 of the insect controlsheets. The matrix material constituting the toxin-containing matrixlayer 130 are the same as that of the third material for theinsect-control sheets. The structure of the pure matrix layer 120 is thesame as that of the pure matrix layer 20 of the insect control sheets.The material constituting the pure matrix layer 120 are the same as thatof the second material for the insect-control sheets.

FIG. 9 is a sectional view illustrating the transfer sheet forfabricating the insect control article.

The transfer sheet 70 is fabricated by layering the toxin-containingmatrix layer 130, the pure matrix layer 120 and the adhesive layer 60 inthe order on one surface of the transfer-sheet substrate 71. Thematerials of the layers are the same as those mentioned in thedescription of the insect control article 6.

Examples of the transfer-sheet substrate 71 include a sheet of polyvinylalcohol (PVA). The insect control article 6 can be fabricated byfloating the transfer sheet 70 on water surface and pressing the body117 against the transfer sheet to transfer the layers from the sheet tothe body. The PVA dissolves in water to disappear.

The transfer sheet 70 is capable of forming insect control layers on thebody 117 having a curved surface.

The transfer sheet 70 mentioned by reference to FIG. 9 is a so-calledwater transfer sheet. The transfer sheet for fabricating the insectcontrol article may be a transfer sheet ordinary used for transferprinting in the air. A film finished with a release agent may beemployed for the substrate of such transfer sheets.

Examples of materials used for the transfer-sheet substrate includesheets of resins such as polypropylene resins, polyethylene resins,polyamide resins, polyester resins, acrylic resins, polyvinyl chlorideresins, polycarbonate resins, polyurethane resins, polystyrene resinsand acetate resins; cellulose sheets such as glassine paper, coatedpaper, and cellophane; and sheets of the composite of these materials.

The transfer sheet 70 may be used to fabricate the insect controlsheets.

The insect control sheets and articles mentioned above may include thetoxin-containing layer and/or the pure matrix layer containing feedsliked by harmful insects, such as yeast. Such layers attract harmfulinsects near the insect control sheets and articles to improve theeffect of insect control.

REFERENCE SIGNS LIST

-   1 a: First insect control sheet-   1 b: Second insect control sheet-   1 c: Third insect control sheet-   1 d: Fourth insect control sheet-   1 e: Fifth insect control sheet-   1 f: Sixth insect control sheet-   1 g: Seventh insect control sheet-   1 h: Eighth insect control sheet-   1 i: Ninth insect control sheet-   6: Insect control article-   10: First sheet substrate-   10 a: Bubble-containing first sheet substrate-   10 b: Top first sheet substrate-   10 c: Bottom first sheet substrate-   11: Bubble-containing second sheet substrate-   12: Hydrophobic part-   13: Hydrophobic part-   15: Air cell-   16: Bubble-   20: Pure matrix layer-   30: Toxin-containing matrix layer-   30 a: Bubble-toxin-containing matrix layer-   51: Cry polyhedron-   56: Bubble-   60: Adhesive layer-   70: Transfer sheet-   71: Transfer-sheet substrate-   117: Body-   120: Pure matrix layer-   130: Toxin-containing matrix layer

1. An insect control sheet floating on water, comprising: a sheet-shapedfirst sheet substrate, a pure matrix layer layered underside the firstsheet substrate; a toxin-containing matrix layer layered underside thepure matrix layer; a floating member for floating the insect controlsheet on water contained in one of the first substrate, pure matrixlayer and the toxin-containing matrix layer, wherein the pure matrixlayer comprises a degradable or water-soluble second material, thetoxin-containing matrix layer comprises a degradable or water-solublethird material and Cry polyhedron that is an insecticidal proteinproduced by Bacillus thuringiensis fixes to a polyheadron of polyhedronprotein, and the toxin-containing matrix layer releases the Crypolyhedron by decomposition or dissolution of the third material, to thewater on which the insect control sheet is floated.
 2. The insectcontrol sheet according to claim 1, wherein the second material iscomposed of the same ingredients as that of the third material.
 3. Theinsect control sheet according to claim 1, wherein the third materialcomprises at least one ingredient selected from the group consisting ofcollagen, gelatin, chitin, chitosan, glycosaminoglycan, hyaluronic acid,chondroitin sulfate, elastin, fibronectin, laminin, fibrin, alginicacid, fibroin, starch, pectin, pectic acid, agarose, heparin,carboxymethyl cellulose, cellouronic acid, polyvinyl alcohol,polyethylene glycol, methyl polymethacrylate, methacrylate esterpolymers, silicone resins, polylactic acid, polyglycolic acid,polye-caprolactone, bovine serum albumin, casein, sucrose, and mixtures,polymers, copolymers and cross-linked products of those substances. 4.The insect control sheet according to claim 1, wherein the first sheetsubstrate comprises a degradable first material, and thetoxin-containing matrix layer and the pure matrix layer degrade ordissolve in water in a shorter time than that required for thedecomposition or dissolution of the first sheet substrate.
 5. The insectcontrol sheet according to claim 1, wherein the first sheet substratecomprises nonwoven fabric or mesh sheet.
 6. The insect control sheetaccording to claim 1, wherein the floating member is bubbles containedin the first sheet substrate.
 7. The insect control sheet according toclaim 1, further comprising a sheet-shaped second sheet substrate thatis layered on a top side of the first sheet substrate, wherein thefloating member is bubbles contained in the second sheet substrate. 8.The insect control sheet according to claim 1, wherein the floatingmember is bubbles contained in the toxin-containing matrix layer.
 9. Theinsect control sheet according to claim 1, wherein the first sheetsubstrate comprises two layers, and the floating member is an air cellbeing formed between the two layers of the first sheet substrate. 10.The insect control sheet according to claim 1, wherein the floatingmeans is a patterned hydrophobic region being formed on the underside ofthe first sheet substrate, and the pure matrix layer andtoxin-containing matrix layer are layered on the part of the undersideof the first sheet substrate where the hydrophobic region is not formed.11. The insect control sheet according to claim 1, wherein the floatingmember is a hydrophobic region being formed on the top side of the firstsheet substrate.
 12. The insect control sheet according to claim 1,wherein a design is made on an underside of the first sheet substrate.13. An insect control article floating on water, comprising: a bodyfloatable on water, a pure matrix layer layered underside the body, atoxin-containing matrix layer layered underside the pure matrix layer;wherein the pure matrix layer comprises a degradable or water-solublefirst material; the toxin-containing matrix layer comprises a degradableor water-soluble second material and Cry polyhedron that is aninsecticidal protein made of Bacillus thuringiensis fixed to apolyheadron of polyhedron protein; and the toxin-containing matrix layerreleases the Cry polyhedron by decomposition or dissolution of thesecond material to the water on which the insect control articlefloated.
 14. A transfer sheet for an insect control sheet or insectcontrol article, comprising: a toxin-containing matrix layer, a purematrix layer, and an adhesive layer layered in an order on one surfaceof a transfer-sheet substrate; and wherein the pure matrix layercomprises a degradable or water soluble first material, thetoxin-containing matrix layer comprises a degradable or water-solublesecond material and a Cry polyhedron that is an insecticidal proteinmade of Bacillus thuringiensis fixes to a polyhedron of polyhedronprotein.